1. Technical Field
The present invention relates to methods for forming ferroelectric capacitors, ferroelectric capacitors and electronic devices.
2. Related Art
Ferroelectric memories are RAMs that use a ferroelectric layer as a capacitor dielectric layer, and attracting attention as RAMs that can read and write at high speed. A ferroelectric capacitor included in such a ferroelectric memory has a structure in which a ferroelectric film is formed between a lower electrode and an upper electrode, and can be formed by patterning with dry etching. An example of related art is described in Japanese Laid-open Patent Application JP-A-2003-243623.
When the ferroelectric capacitor described above is formed, the ferroelectric layer may be damaged when the upper electrode is formed, or when dry etching is conducted for patterning. Such damage may destroy the crystal structure of the ferroelectric layer, which would lead to deterioration of the electrical characteristics of the ferroelectric capacitor. For this reason, heat treatment for recovering the crystallinity of the ferroelectric layer may be conducted after patterning is completed. In order to sufficiently recover the crystal structure in the heat treatment, it is necessary to increase the heat treatment temperature to a higher level, or conduct the heat treatment for a longer period of time. However, in either of the cases, compositions (for example, Pb) composing the ferroelectric layer may evaporate, or diffuse into the lower electrode and the upper electrode. This may also lead to deterioration of the electrical characteristics.